I. Field of Invention
The present invention relates to a quantification device for quantifying the relative contents of two isotopes of at least one specific gaseous constituent contained in a gaseous sample from a fluid, of the type comprising a means for forming a gaseous flow from the sample, comprising means for separation by means of selective retention of the or each specific gaseous constituent, a means for quantifying the relative contents of the two isotopes to be analysed of the or each specific constituent.
This device is used in particular to analyse the gases extracted from a petroleum fluid produced in an oil well or to determine extracted gas composition from a drilling fluid.
II. Description of the Related Art
In the last case, when an oil or other outflow well is drilled (in particular gas, vapour, water), it is known to carry out an analysis of the gaseous compounds contained in the drilling mud originating from the well. This analysis allows the geological sequence of the formations passed through during the drilling operation to be reconstructed and is used to determine the possible applications of the fluid deposits encountered.
This analysis, which is carried out in a continuous manner, comprises two main phases. The first phase consists in extracting the gases carried by the mud (for example, hydrocarbon compounds, carbon dioxide, hydrogen sulphide). The second phase consists in qualifying and quantifying the extracted gases.
In order to extract the gases from the mud, a degassing means with mechanical agitation of the type described in FR 2 799 790 is often used. The gases extracted from the mud, mixed with a carrier gas which is introduced into the degassing means, are conveyed by means of suction through a gas extraction pipe to an analysis device which allows the extracted gases to be quantified.
The analysis device comprises a gas-phase chromatograph (GPC) which allows the various gases collected in the degassing means to be separated in order to be able to quantify them.
In some cases, however, it is necessary to carry out a more precise analysis of the gaseous content of the extracted gases, using a device for measuring the relationship between the contents of carbon isotopes 13C and 12C in the gaseous hydrocarbon compounds extracted from the mud.
A device of this type comprises, in conjunction with the gas-phase chromatography, a combustion oven and an isotope ratio mass spectrometer (IRMS) which is intended to analyse the outflow from the combustion oven.
A device of this type is unsatisfactory, in particular when the analysis must be carried out on a drilling site or on a production site. The IRMS must be kept in a vibration free environment under pressure and temperature conditions which are substantially constant in order to obtain precise and repetitive measurements. Consequently, it is necessary to carry out an “off-line” analysis of the samples in a climate-controlled laboratory. If it is desirable to carry out the analysis “on-line”, however, it is necessary to bring a large, fragile and complex climate control and an IRMS control assembly close to the well in an environment which can be hostile and inaccessible.